1. Field of the Invention
This invention relates generally to semiconductor manufacturing, and, more particularly, to a method and apparatus for performing a periodic calibration of metrology data results.
2. Description of the Related Art
The technology explosion in the manufacturing industry has resulted in many new and innovative manufacturing processes. Today""s manufacturing processes, particularly semiconductor manufacturing processes, call for a large number of important steps. These process steps are usually vital, and therefore, require a number of inputs that are generally fine-tuned to maintain proper manufacturing control.
The manufacture of semiconductor devices requires a number of discrete process steps to create a packaged semiconductor device from raw semiconductor material. The various processes, from the initial growth of the semiconductor material, the slicing of the semiconductor crystal into individual wafers, the fabrication stages (etching, doping, ion implanting, or the like), to the packaging and final testing of the completed device, are so different from one another and specialized that the processes may be performed in different manufacturing locations that contain different control schemes.
Generally, a set of processing steps is performed on a group of semiconductor wafers, sometimes referred to as a lot, using a semiconductor manufacturing tool called an exposure tool or a stepper. Typically, an etch process is then performed on the semiconductor wafers to shape objects on the semiconductor wafer, such as polysilicon lines, each of which may function as a gate electrode for a transistor. As another example, a plurality of metal lines, e.g., aluminum, may be formed that serve as conductive lines that connect one conductive region on the semiconductor wafer to another. The manufacturing tools communicate with a manufacturing framework or a network of processing modules. Each manufacturing tool is generally connected to an equipment interface. The equipment interface is connected to a machine interface to which a manufacturing network is connected, thereby facilitating communications between the manufacturing tool and the manufacturing framework. The machine interface can generally be part of an advanced process control (APC) system. The APC system initiates a control script, which can be a software program that automatically retrieves the data needed to execute a manufacturing process.
FIG. 1A illustrates a typical semiconductor wafer 105. The wafer 105 typically includes a plurality of individual semiconductor die arranged in a grid 150. Photolithography steps are typically performed by a stepper on approximately one to four die locations at a time, depending on the specific photomask employed. Photolithography steps are generally performed to form patterned layers of photoresist above one or more process layers that are to be patterned. The patterned photoresist layer can be used as a mask during etching processes, wet or dry, performed on the underlying layer or layers of material, e.g., a layer of polysilicon, metal or insulating material, to transfer the desired pattern to the underlying layer. The patterned layer of photoresist is comprised of a plurality of features, e.g., linetype features, such as a polysilicon line, or opening-type features, that are to be replicated in an underlying process layer.
Turning now to FIG. 1B, once at least one manufacturing process is performed upon the semiconductor wafers 105, a metrology tool 350 is used to perform a metrology data acquisition process. The metrology tool 350 acquires metrology data from the processed semiconductor wafers 105. Accuracy of the results acquired by the metrology tool is very important. Metrology data provides information relating to the quality of the processes performed on the semiconductor wafers, the condition of the semiconductor wafers 105 being processed, and information relating to the performance of the devices produced from the processed semiconductor wafers 105. Often, data from the metrology data acquisition process is used to perform adjustments to other manufacturing processes performed on the semiconductor wafers 105. Also, metrology data is used to predict errors that may occur on semiconductor wafers 105 that are subsequently processed. The predicted errors are then used to calculate control parameters for a manufacturing tool during subsequent processing of semiconductor wafers 105.
Many times, metrology tools 350 operate with a slight amount of measurement variation from one time period to another. For example, a particular metrology tool 350 may produce slightly different measurement results from one day to another. Often, environmental factors, such as temperature, pressure, etc., can vary from day to day, causing variations in the operation of the metrology tools 350. Furthermore, other undetectable random variations in the operation of the metrology tools 350 can occur from one time period to another. These variations can cause errors in adjustments made to manufacturing operations during an attempt to compensate for measured errors. For example, metrology tools 350 may be used to measure the critical dimensions (CD) of a feature formed on a semiconductor wafer using a photolithography process. Based upon the CD measurements, adjustments to the photolithography process, such as exposure time, exposure light intensity, etc., are made to compensate for any CD errors detected. Since critical dimension data are represented by very minute measurement, any errors in the CD data can result in significant errors in the overall structures of the features on semiconductor wafers 105. Due to variations in the accuracy of the metrology tool 350 from one time period to another, quality and operation of devices produced from the processed semiconductor wafers 105 can significantly vary from one time period to another.
The present invention is directed to overcoming, or at least reducing the effects of, one or more of the problems set forth above.
In one embodiment of the present, a method is provided for performing periodic correction of metrology data. At least one semiconductor wafer is processed. Metrology data from the processed semiconductor wafer is acquired. At least one test wafer is processed. Test wafer metrology data from the processed test wafer is acquired. A test wafer metrology calibration process is performed upon the acquired metrology data using the acquired test wafer metrology data to produce a calibrated metrology data. At least one control input parameter adjustment is performed for subsequent manufacturing processes based upon the calibrated metrology data.
In another embodiment of the present invention, a system is provided for performing periodic correction of metrology data. The system of the present invention comprises: a metrology tool adapted to acquire metrology data from a processed semiconductor wafer; a metrology tool database electronically coupled to the metrology tool, the metrology tool database being adapted to store metrology data; a test wafer database electronically coupled to the metrology tool, the test wafer database being adapted to store test wafer metrology data; and a process control electronically coupled with the metrology tool database and the test wafer database, the process control being adapted to acquire data from the metrology tool database and the test wafer database to calibrate the metrology data and determine at least one control input parameter for processing a semiconductor wafer.